2. Hemostasis and Blood Coagulation Flashcards
Coagulation and Dentistry • Tooth Extraction-Up to 10% of extraction wounds heal improperly: • Further complicated by: – Poor general health (\_\_\_\_, Vitamin C and \_\_\_\_ deficiency) – Compromised \_\_\_\_ Function – Genetic \_\_\_\_ Disorders – Patients on Anti-\_\_\_\_
* Blood coagulation depends on Vit K, C and folate deficiency - complicate extractions and contribute to bleeding disorders * Alcoholics, individuals on medications, hepatitis patients, HIV/AIDs, fasting, albumin-issues, potent chemotherapies - compromised liver function
vitamin K folate liver hemorrhagic coagulants
• Hemostasis- a series of regulated processes that maintain blood
in a ____, ____STATE in normal vessel while rapidly forming a ____ PLUG, at the site of vascular injury.
* Series of processes that allow blood to be fluid and clot-free when there is no injury - mostly anti-coagulants/anti-aggretory * However, when site of injury > very quickly need to form localized hemostatic plug (liquid into a solid structure) > involves a series of pro-coag/pro-agg compounds * When balance shifts > various problems > hemostasis goes awry
fluid
clot-free
localized hemostatic
When hemostasis goes awry
• Hemorrhagic disorders- characterized by excessive bleeding, hemostatic mechanisms are either ____ or insufficient to prevent normal blood loss.
• ____ disorders- blood clots (thrombi) that are formed within intact blood vessels or within chambers of the heart- discuss in more detail in Thrombosis-Embolism.
• Pro-aggretory mechanisms here are inhibited - hemorrhagic disorders • Thrombotic - not necessarily at a site of \_\_\_\_, obstruct vasculature, leading to complications ○ Increase in pro-aggretatory vs. anti > thrombus formation
blunted
thrombotic
injury
Normal Clotting In Response to Injury
Relies on complex interaction between all three components:
- ____- Endothelium and underlying ECM.
- ____
- ____ Cascade• Platelets form the ____
vascular wall
platelets
coagulation
platelet plug
Coagulation is initiated by…..
• ____ to the vascular wall and surrounding tissue.
• Contact of blood with damaged ____
Stages of Hemostasis
• Vasoconstriction (____ phase)- Transient
• Platelet Activation Phase-Formation of a ____
• Coagulation Phase – coagulation phase activation, ____ and ____ formation.
• Fibrinolytic Phase: Clot ____ and ____
• This process occurs in four distinct stages… • Do not want to vasoconstrict for a period of time • Platelet plug is stabliized via fibrin mesh and clot - utilizes a coagulation cascade ○ Coagulation is \_\_\_\_ phase, platelet activation is \_\_\_\_
trauma
endothelium
vascular platelet plug fibrin mesh clot stabilization resorption
second
primary
Vascular Phase: Vasoconstriction
• Contraction results from
– ____ reflexes- by pain nerve impulses
– ____-
contraction of blood vessels- vascular spasm
– Local humoral factors- platelet release of vasoconstrictor ____
• Vasoconstriction- reduces flow of blood from vessel rupture
* Locally - TXA2, and \_\_\_\_ results in vasoconstriction * Recruit \_\_\_\_ to that site of injury
nervous local myogenic spasm TXA2 endothelin platelets
First responders - platelets
Auto-catalytic
Resting platelet:
• Small (1-4 micrometers in diameter), ____, circulating, smooth discs derived from ____,
• Normal concentration in blood is ____ mg/dL
• Half-life in blood ____ days.
Activated platelet:
Adhere to ____ and ECM (collagen, fibronectin, proteoglycans) and change ____
Activation-Secrete ____ containing pro- coagulants
Aggregate to form a platelet plug and provide catalytic surface
* Von willibron factor - protein that is utilized during \_\_\_\_ * These processes happen \_\_\_\_, and it's \_\_\_\_
anuclear
megakaryocyte
150,000-450,000
8-12
vWF
shape
granules
adherence
simultaneously
auto-catalytic
- Injury
- Adhesion:
➢____
➢-Collagen - Activation:
➢____ Changes
➢Granule Secretion ➢____ loops
4. Aggregation: ➢\_\_\_\_ ➢Thrombin production ➢\_\_\_\_
• Thrombin cleaves \_\_\_\_ into fibrin - going from a mechanical plug, to a more \_\_\_\_ mesh that has fibrin holding it down
von willebrand factor (vWF) membrane feedback vWF fibrinogen
fibrinogen
organized
Adhesion- process by which platelets adhere to damaged regions of vessels
• Interaction between platelet Surface receptor (____) and ____. Platelet GpIIb-IIIa- bind ____
• Interaction between platelet receptor and exposed collagen
– vWF stabilizes interaction with collagen against ____ of blood flow
– vWF acts as ____ for platelets followed by adherence of platelets to ECM
• vWF binds to specific integrin on platelet (\_\_\_\_) > in presence of ADP > platelets expose second integrin (\_\_\_\_), which is a receptor for fibrinogen • 3 common deficiencies in these factors - deficiency in vWF ○ Not able to catch \_\_\_\_ - you're going to have increased bleeding ○ Deficiency in \_\_\_\_ (Glosmon etc. etc.) § Increased bleeding ○ Deficiency in integrin that is binding \_\_\_\_ (Bernand-Solar?) § Increased bleeding ○ Deficiency in \_\_\_\_ is most common
GpIb vWF fibrinogen shear forces catcher
GpIb GpIIb-IIIa catching integrin vWF vWF
Platelet Activation- process by which platelets respond to binding ECM
Results in
➢ Shape change- ____ spiny spheres.
➢ Formation of activated surface
➢ Secretion of granules in response to activation.
➢ Granules (____ and ____-granules) contain
– ____, ATP, ____, calcium
– ____ factors
– ____ factors
• Inactive state - platelets contain granules - dense and alpha • As they begin to adhere and activated, they secrete the contents of their granules ○ ADP - potent \_\_\_\_ agent - beacon to all other platelets ○ TXA2 - \_\_\_\_, minimal ○ \_\_\_\_ - coaggulation cofactors ○ GF - reform the \_\_\_\_
sticky dense alpha ADP TXA2 coagg growth
pro-agg
vasoconstrictor
Ca++
endothelium
Platelet Aggregation- process by which platelet plug is formed prior to fibrin stabilization.
- Sets the process of thrombin processing fibrinogen to ____ in motion
- GpIIb-IIIa on platelets binds ____ forming a bridge between adjacent platelets. Concurrently-there is an activation of thrombin via ____ complex
- Bring the fibrinogen with them, in order to form the fibrin
- Bound to the collagen, and they have spiky “hands” > start pulling in two sides of site of injury to try to organize the area and make a stable clot
- Platelet surface is going to form the surface onto which ____ binds, as the last step in the coagulation cascade
fibrin
fibrinogen
pro-thrombinase
pro-thrombin
Primary Hemostasis-Formation of a platelet plug
• At injury, platelets bind collagen, caught by ____, collagen activates platelets, platelets change shape, release granules, ____ is a potent pro-agg compound, ____ is a mild vasoconstrictor and is pro-agg
• The entire surface is geared to recruit more platelets
• As aggregate, they form a ____ plug
vWF
ADP
TXA2
hemostatic
Aggregation: a delicate balance between Endothelium and platelets
➢ Endothelium produces Anti-aggregatory agents.
➢ ____
➢ ADPase
➢ Platelets secrete- Pro-aggregatory agents.
➢ ____
➢ ADP (at high levels feeds back to stimulate ____)
• You don't want platelets aggregating upstream or downstream of inflammatory - do not want clots here - vessel occlusion • Endothelium itself has anti-agg properties ○ Doesn't have EC collagen exposed ○ Synthesizes prostacyclin - anti-agg compound ○ Synthesizes ADPase - cleaves ADP • Balance of focusing pro-agg at only at site of injury, and the rest of the endothelium maintains its anti-agg properties • The platelets secrete pro-agg ○ TXA2 and ADP
prostacyclin (PGI2)
TXA2
PGI2
Coagulation Cascade
What causes initiation of the coagulation cascade?
____ to the vascular wall and surrounding tissue release of tissue factor.
Contact of blood with damaged ____.
- Basic Principle: each reaction depends on the assembly of an ____ (an activated coagulation factor), a ____ ( a pro-enzyme form of the next coagulation factor in the series) and a ____ ( a reaction accelerator- often ____)
- Assembled on a phospholipid surface either the ____ surface or the ____ surface.
- Release of TF, and contact of blood (contains factors that are activated by TF to form thrombin)
- Phospholipid surface = ____ surface
trauma endothelium enzyme substrate cofactor Ca++
endothelial
platelet
platelet
• Two pathways: Intrinsic (in vitro) and Extrinsic
– ____ delineation
– ____ between two pathways
• Two pathways converge at common factor- ____ to form the prothrombinase complex. End result is production of thrombin which catalyzes cleavage of fibrinogen to ____
• Extrinsic Pathway- Most ____ Relevant
– Begins with trauma to the vascular damage and release of ____ which activates pathway
– Explosive- in severe tissue trauma clotting occurs within ____ seconds
artificial
cross-talk
factor X
fibrin
physiologically
tissue factor
15
• Intrinsic pathway > in-vitro pathway > used to test for various properties for individuals with disease
• Not separate and distinct, but an artificial delineation, and there is cross-talk
• In order to activate extrinsic > TF is generated at endothelium; the factors that are downstream are all contained in the ____
• Two forms of factors; inactive forms (red) and active forms (green)
○ Inactive: ____ > activated F8
• Complexes that require phospholipid surface are in yellow
○ Also require ____; the platelets themselves secrete Ca in the granules
• Extrinsic pathway (same time as plug forming) activated with release of TF; occurs with 10-15s > TF activates inactive ____ into active F10, it also activates ____ (if it’s in the intrinsic pathway) > activated F10 is going to (on surface of ____) is going to activate ____ > combination of F10 and F5 form complex that ____ binds to > activated to thrombin > activates fibrin from fibrinogen > fibrin forms a stable covalent mesh through the activity of ____
○ These processes from F10 to the formation of thrombin, all happen on the surface of the ____ plug
○ Fibrinogen is sitting within the platelet plug
blood F8 Ca++ F10 F7 platelet F5 pro-thrombin F13 platelet
Prothrombinase Complex- also known as Prothrombin Activator
• Activates ____ - acts a holder for ____; and on other side it holds ____
• F10 - ____ - cleaves the pro-thrombin to generate thrombin
• All happens on surface of ____ plug
• This whole structure corresponds to …
• Thrombin feeds back and activates aspects of ____ cascade in order to form the fibrin mesh
• Therefore, ____ also activates other coagulation factors
F5 F10 pro-thrombin protease platelet co-agg fibrin
Thrombin cleaves fibrinogen to form clot
• Fibrinogen is a \_\_\_\_-peptide, and it has a N-terminal region, and it has a series of \_\_\_\_ charged peptides (repel each other) > these peptides are cleaved by \_\_\_\_ • Thrombin cleaves negatively charged peptides > fibrin monomers than in a staggered array sit on top of the platelet plug • In terms of vasculature, taken jelly-like plug stabilized with fibrin ○ Blood flow is less \_\_\_\_ (endothelin levels are decreased, and TXA2 are lowered) > you want normal blood flow again • \_\_\_\_ array of fibrin > soft clot > can be washed away, but the fibrin dimers are \_\_\_\_ linked > true, chicken-mesh, covalent fibrin mesh > allows you to heal \_\_\_\_, and allows it not to be washed away by blood flow ○ Linked by Vit K dependent transglutaminase - \_\_\_\_ • Compromised transglutaminase activity ○ Vit K - lipid soluble ○ Patients with \_\_\_\_ surgery, and \_\_\_\_ diets ○ Synthesized in \_\_\_\_ • What might be consequence of inability to form fibrin polymer ○ \_\_\_\_ - require the covalently linked polymer mesh
tri negatively thrombin vasoconstricted staggered covalently wound
F13
bariatric
unhealthy
liver
bleeding/bruising
Secondary Hemostasis-Deposition of Fibrin
• TF > F10 (extrinsic) > phospholipid surface is formed by platelet plug, and the surface allows pro-thrombin to be convert to thrombin > fibrinogen to fibrin > fibrin must be polymerized by activated \_\_\_\_ (vit-K dependent transglutaminase)
F13
Clot retraction-Serum vs Plasma
• Clot begins to retract ____ minutes after formation.
• Platelets contribute to retraction by contracting platelet ____ attached to fibrin thus the edges of the broken blood vessel are pulled closer together for repair.
• Fluid exuded from the clot within ____ minutes- this fluid is called ____- most ____ and ____ factors have been removed.
2-3 spicules 20-60 serum fibrinogen clotting
Plug Dissolution
• Do not want to keep fibrin mesh in circulation bc after site of injury is healed it becomes a ____ of immune cells, RBCs, which can propagate to form a ____ (clot that forms in an area where you don’t have site of injury, or where you have not dissolved a plug)
• Dissolution of plug relies on ____ (protease), platelets bring these in with fibrinogen
○ Plasminogen is inactive, it is activated to ____, which then takes and degrades the fibrin mesh to give fibrin degradation products
“catcher”
thrombus
plasminogen
plasmin
Fibrinolysis- Lysis of clots
• ____ cells produce tissue plasminogen activator tPA – Converts plasminogen to plasmin a day or so after vessel injury
– Plasmin is a ____ that degrades polymerized fibrin
• Free plasmin is bound and neutralized by ____
• t-PA activity is blocked by endothelial produced ____
– PAI is induced by thrombin and cytokines and therefore play a role in ____ processes of the vasculature
* Fibrinolysis - during this process the endothelium becomes \_\_\_\_ * Don't want this to happen too quickly - want time to \_\_\_\_
endothelial
protease
plasminogen inhibitor type 1 and type 2 (PAI)
PAI
inflammatory
pro-fibrinolytic
heal
Regulation of Plasmin Levels
Plasmin inhibited by ____
• Primary platelet plug, covered with fibrin mesh • Endothelium release TPA > activates plasminogen > plasmin > breaks down the fibrin > fibrin-degradation products > weak anti co-agg (inhibiting the upstream coagg cascade) • TPA is regulated by \_\_\_\_ ○ Determines how quickly plasminogen is activated, and the free plasma levels are tempered/decreased by \_\_\_\_, so the clot is broken down at a regulated appropriate rate
anti-plasmin (AP)
PAI
anti-plasmin
Fibrinolytic Phase- counter-regulatory mechanisms limit hemostatic plug to site of injury
Intravascular anti-coagulants
• Thrombomodulin-integral protein of ____- binds 85 % of free ____ thus inactivating it
• Anti-thrombin III. Bind remaining ____, inhibits several enzymes of coagulation cascade.
• Heparin-____- potentiates anti-thrombin III. Low levels in blood when binds to anti-thrombin III increases its activity ____ fold. Abundant in lung where there is ____ venous blood flow
* More RBC in veins because it's much slower, in the arteries there are fewer, there are more WBC*** * In addition to fibronolysis, there are intravascular anti-coagulants that inhibit various aspects of the coagg cascade * Thrombomodulin - lets \_\_\_\_ take precedence over coagg (binds 85% of thrombin) * Heparin - don't do much, but when bind ATIII > they increase their activity
endothelium thrombin thrombin proteoglycan 1000 slow
fibrinolysis
